1. Technical Field
This application relates to mobile telecommunications systems in general, having particular application in mobile telecommunications device operable with a plurality of radio access networks in general, and in particular relates to an apparatus and a method for handling inter-radio access technology measurement requests in a mobile telecommunications device.
2. Description of the Related Art
In a typical cellular radio system, mobile user equipment communicates via one or more cellular radio access networks (RANs) to one or more core networks. User equipment (UE) comprises various types of equipment such as mobile telephones (also known as cellular or cell phones), lap tops with wireless communication capability, personal digital assistants (PDAs) etc. These may be portable, hand held, pocket sized, installed in a vehicle etc and communicate voice and/or data signals with the radio access network.
UMTS (Universal Mobile Telecommunications System) is known as a third generation (3G) system in which the radio access network is known as UMTS Terrestrial Radio Access Network (UTRAN). E-UTRAN is another radio access network. GERAN (GSM EDGE Radio Access Network) is a second generation (2G) system, based on GSM, which was developed to provide improved data access compared with GSM.
In the following, reference will be made to GERAN, GSM EDGE, GPRS, UTRAN, E-UTRAN and UMTS and to particular standards. However it should be understood that the invention is also applicable to other mobile telecommunications system.
A cellular radio access network covers a geographical area typically divided into a plurality of cell areas. Each cell area is served by at least one base station, which in UMTS may be referred to as a Node B and in GSM is referred to as base station (BS). Each cell is typically identified by a unique identifier which is broadcast in the cell. The base stations communicate at radio frequencies over an air interface with the radio devices within range of the base station. Several base stations may be connected to a radio network controller (RNC) which controls various activities of the base stations. The radio network controllers are typically connected to a core network.
Also available are so-called Generic Access Networks (GANs). These are typically not wide area cellular systems as described above but are local access networks systems, for instance implemented with access devices (typically with a wireless interface with the user equipment) that comply with IEEE standards 802.xx (e.g. WiFi hotspots, Wireless Local Area Networks or broadband wireless routers, for instance in office or domestic premises). GAN technology provides an access network to the mobile core network that can be used to access the existing circuit-switched and packet-switched services. Generally, the provision of the generic access network is based on use of unlicensed spectrum (e.g. WLAN) and IP-based broadband access network for instance as set out in IEEE 802.xx standards. GAN enables typical wireless telecommunications services to be delivered at homes or in offices. The intention is for end users to enjoy the same service as with the wide area cellular network(s) but access it via a local access point such as a broadband wireless router. Fixed/mobile convergence may therefore be provided.
Various standardization bodies are known to publish and set standards for mobile telecommunication systems, each in their respective areas of competence. For instance, the 3GPP (Third Generation Partnership Project) publishes and sets standards for GSM (Global System for Mobile Communications) based UMTS, and the 3GPP2 (Third Generation Partnership Project 2) publishes and sets standards for CDMA (Code Division Multiple Access) based UMTS. 3GPP Release 8 introduces LTE (Long Term Evolution) and E-UTRAN. 3GPP also publishes and set standards for GAN systems. Within the scope of a particular standardization body, specific partners publish and set standards in their respective areas.
The 3GPP specification TS 43.318 v8.4.0 (hereby incorporated by reference in its entirety) relates to the Generic Access Network, an access network providing access to A/Gb or Iu interfaces via an IP network. The 3GPP specification TS 44.318 v8.5.0 (hereby incorporated by reference in its entirety) relates to the Generic Access Network: Mobile GAN interface layer 3 specification and Annex E relates to GAN Specific Requirements for Interworking with UTRAN. The 3GPP specification TS 25.331 v5.23.0 (hereby incorporated by reference in its entirety) relates to the Protocol Specification for Radio Resource Control (RRC) of the UMTS Radio Access Network and Section 14.3 relates to inter-RAT measurements and Section 14.3.1.1 provides a description of an inter-RAT reporting event known as Event 3A, configured when the estimated quality of the currently used UTRAN frequency is below a certain threshold and the estimated quality of the other system is above a certain threshold.
Consider a wireless mobile device, generally referred to as user equipment (UE) or a mobile station (MS), that complies with the 3GPP specifications for the UMTS protocol and the specifications for the GSM EDGE protocol and the specifications for the GAN protocol. Such a MS may be connected to the 3G network, the 2G network or the GAN. In accordance with Annex E.1 of the 44.318 specification, when the MS is in GERAN/UTRAN preferred mode (also referred to as cellular preferred mode) and an event 3A has been configured, the MS shall only send a measurement about the GAN cell to trigger handover when no GERAN cells from the Inter-RAT measurement object list satisfy the triggering condition of the configured Event (as described in TS 25.331).
There are thus proposed strategies for handling inter-radio access technology measurement requests in a mobile telecommunications device. A number of such strategies are detailed below.
Other aspects and features of the proposed strategy will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of an apparatus and method for handling inter-radio access technology measurement requests in a mobile telecommunications device.
Where the same reference numerals are used in different figures, these are used to denote similar elements.